1. Field of the Invention
The present invention relates to diffused junction capactiors and processes for forming the same.
2. Description of Prior Art
It is well known in the prior art to form variable capacitance diodes and the like utilizing diffusion techniques where, for instance, a P-N junction is formed by first diffusing a donor dopant into a substrate and thereafter diffusing an acceptor dopant into the substrate. For instance, as disclosed in U.S. Pat. No. 3,392,067, Horiba et al., an N-type region is first formed in a silicon substrate by diffusing bismuth into a silicon wafer. Therafter, boron is diffused through the N-type region into the wafer until the surface density of the boron reaches a higher order of magnitude than the bismuth density, thus forming in the wafer a P-type region which, together with the N-type region, forms a hyper-abrupt junction.
This type of procedure, however, enables only the formation of a single P-N junction, and does not provide a process wherein separate isolation diffusion is not necessary.
The present invention overcomes both of the above faults of the prior art, provides a novel double diffused junction capacitor and a novel process for forming the same.